6.3. SR 10-15-2018 - Laserfiche WebLink

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Elk River Watershed 2018 Activities Report Figure 1 also displays the distribution of different land classifications across this watershed, as extrapolated from aerial imagery. Much of the land has been altered from its original state and developed somehow. The water clarity and nutrient content of all streams and rivers change as they continue to flow downstream. As water moves downstream, the area of drainage increases. This in turn also increases the potential for eroding sources to contribute suspended sediments, nutrients, and other pollutants to the water. Thus, higher pollutant levels are expected at downstream versus at upstream locations. A lake such as Lake Orono, at the bottom of this large watershed, would be expected to receive abundant nutrients and sediment due to the tremendous size of the watershed – even if it was in a completely natural state. However, with development comes an increase in the potential for waterway pollution beyond what would normally occur. Of the factors that determine how much pollution enters a stream or river, land use and precipitation are the most important. Land that is highly vegetated (wetlands, forests) reduces erosion and transport of sediment or pollutants because the leaves of plants reduce rainfall impact force, and root systems allow for infiltration of water into the ground. Land that is highly developed (pavement, lawns, bare soil, agricultural fields, etc.) lacks the capacity to quickly infiltrate water so more water runs off the land and carries soil or pollutant particles with it. Of the 613 square miles in the Elk River Watershed, roughly 27% would be considered agriculture, 20% forests, 18% pasture/grass, 17% wetlands, and single-digit percentages of residential and urban areas. When this area receives a small amount of rain (less than 1 inch for example) a portion of this water runs off the landscape and feeds the lakes and streams, while the rest is infiltrated. However, during larger rain events the amount of water that hits the landscape overcomes the infiltration capacity. More runoff occurs, wetlands fill and spill over, and soil erosion becomes visible from bare soil locations. The Elk River and other streams respond by increasing in height, increasing in velocity, and changing color from clear or transparent to a darker muddy color. This is an indication of the soil that was once on the landscape that is now being transported down the river. The development of the watershed has unfortunately resulted in the impairment of several water resources. Section 303(d) of the Federal Clean Water Act requires the Minnesota Pollution Control Agency (MPCA) to identify waterbodies that do not meet water quality standards and to develop pollutant Total Maximum Daily Loads (TMDLs) for these waterbodies. A TMDL is the amount of a pollutant that a waterbody can assimilate without exceeding the established water quality standard. Based upon their use class (Table 1), MPCA has identified the specific impairment parameters, affected use areas, and required pollutant reductions within these waterbodies (Table 2 and 3, Map 1). In completing these studies, pollutant contributions and recommended reductions are included from both point sources (wastewater treatment facilities) and non-point source areas (rural landscapes and stormwater). Table 1. Beneficial Use Classes for Minnesota Waters. Adapted from MN Admin Rules Chp. 7050.0140 Class 1: Domestic Consumption Sources of supply for drinking, culinary or food processing Class 2: Aquatic Life / RecreationFish, amphibians, bathing, boating, or other recreation Class 3: Industrial Consumption Industrial processes, cooling water, commercial purposes Class 4: Agriculture & Wildlife Stock watering, irrigation, waterfowl or wildlife habitat Class 5: Aesthetics & NavigationTransportation, fire prevention, navigation Class 6: Other Uses & Border Waters Other uses not listed, waters bordering states or nations Class 7: Limited Resource Value Intermittent or low flow waters, protected for secondary use 2